The series of L-Leu 1-20-mers, peptides carrying 1-5 N-terminal Gly residues, and oligomers of (S)-beta(3)-Leu and (1R,2R)-2-aminocyclohexanecarboxylic acid were synthesized on TentaGel S NH(2). Five L-Leu residues were found sufficient to catalyze the Juliá-Colonna epoxidation of chalcone with 96-98% ee. Experiment and molecular modeling suggest that catalysis is effected by binding of the enone to the N-terminus, and the helicity of the peptide determines the epoxide configuration through face-selective delivery of a hydroperoxide anion. [reaction: see text]

Enantiomerically pure trans-2-aminocyclohexanecarboxylic acid is an important building block for helical β-peptides. We report here that this amino acid can be obtained from transcyclohexane-1,2-dicarboxylic acid in good yield by a simple one-pot procedure comprising cyclization to the anhydride, amide formation with ammonia, and a subsequent Hofmanntype degradation with phenyliodine(III) bis(trifluoroacetate) (PIFA) as the oxidant. The N-Fmoc-and N-BOC-protected derivatives were obtained by treatment of the amino acid with Fmoc-OSu and BOC 2 O, respectively. The N-BOC derivative could be prepared in even better overall yield by a onepot procedure leading directly from trans-cyclohexane-1,2-

The copper enzyme galactose oxidase (GOase, EC 1.1.3.9) catalyses the oxidation of D-galactose and other primary alcohols in air to the corresponding aldehydes and hydrogen peroxide. The current mechanistic hypothesis for this two-electron redox reaction involves a Cu(I)/Cu(II) couple and the reversible oxidation of a ligating phenolate (tyrosine residue of the Tyr272-Cys228 conjugate) to a phenoxyl radical. Our approaches to functional models for galactose oxidase comprise both the use of low-molecular-weight copper complexes of a Schiff-base and sulfonamide ligands, and the synthesis/screening of combinatorial libraries. With regard to the latter, we have synthesized (by the IRORI-directed synthesis approach) peptide libraries carrying either His or the redox-active amino acids Tyr, mod-Cys (a model for the Tyr272-Cys228 conjugate) or TOAC (a TEMPO-derived alpha-amino acid) at four variable positions. After incubation with copper ions, the catalytically active library members were identified by specially designed screening methods.